基于改进烟花算法的非线性模拟电路测试激励优化

为增强非线性模拟电路故障诊断中故障模式之间的可辨识性,提高故障诊断率,提出一种基于改进烟花算法的非线性模拟电路测试激励优化方法。该方法首先采用基于Volterra频域核和BP神经网络的方法对非线性模拟电路进行建模,进而针对烟花算法存在寻优速度慢、效率低等问题,对其爆炸算子、变异算子、选择策略等进行改进,采用改进后的烟花算法对非线性模拟电路的测试激励进行寻优,通过电路仿真表明,优化后的信号可有效提高故障可分性,从而提高故障诊断率。     

参量激励孤子的相互作用问题

参量激励孤子的相互作用问题王新龙（南京大学声学研究所南京·２１００９３）１引言最新的研究表明，不同物理媒质中的很多非线性共振现象均可由以下带阻尼的参量驱动非线性Ｓｃｈｒｏｄｉｎｇｅｒ（ＰＤＮＬＳ）方程来描述［１］ｉ（τ＋α）＋ｘｘ＋（β＋｜｜...     

超声造影剂的非线性参量研究

近年来对超声造影剂的研究兴趣日趋增加是由于它有可能改进超声临床诊断的效果，含有微气泡的液体可用和有效的超声造影剂，液体中气泡的存在提高液体的非线性参量值，本文用检测二次谐波的方法实验上测定了５种超声造影剂的非线性参量，四种含气泡的液体（声振后）和半乳糖Ｅｃｈｏｖｉｓｔ３００。结果表明，含有微气泡的液体具有非常大的非线性参量值，对这种高非线性值的现象文中进行了可能的解释和讨论。     

超声造影剂SDA的巨非线性参量

1　引　言近年来 ,含微气泡液体的非线性声学特性引起了人们极大的兴趣。液体中的空气泡是很好的声散射体 ,能产生强的超声散射信号。液体中气泡的非线性振动 ,尤其是在它们的共振频率附近的非线性振动 ,使得它们的存在能够增强液体的声学非线性效应。因此 ,研究含有微气泡的液体的非线性声学特性是非线性声学领域也是它的应用领域的一个重要课题。例如 ,利用含微气泡液体的非线性声特性是水声学中用来增强声参量阵效率的一个有效方法。媒质的非线性声特性可以用非线性声参量 B/A来描述。到目前为止的所有文献上 ,液体、生物流体和组织的非…     

E1 超声造影剂的非线性参量研究

近年来对超声造影剂的研究兴趣日趋增加是由于它有可能改进超声临床诊断的效果。含有微气泡的液体可用作有效的超声造影剂。液体中气泡的存在可提高液体的非线性参量值。本文用检测二次谐波的方法实验上测定了５种超声造影剂的非线性参量：四种含气泡的液体（声振后）和半乳糖Ｅｃｈｏｖｉｓｔ３００。结果表明，含有微气泡的液体具有非常大的非线性参量值。对这种高非线性值的现象文中进行了可能的解释和讨论     

非线性声参量测量中的衍射修正

在超声传播参数的测量中，衍射效应会给测量引来假象．本文结合前文［１］中的实验问题，讨论了衰减及非线性声参量Ｂ／Ａ测量中的衍射修正问题。证明加入此修正后的测得值更加可靠。     

电磁超声脉冲激励电路的设计

为了解决电磁超声能量转化效率较低、信号微弱的问题,设计了一种电磁超声脉冲激励电路。过零检测电路和单片机实现磁场强度与涡流激发的同步以及脉冲个数的控制;UCC3895芯片产生全桥电路的驱动信号,控制脉冲的频率和占空比;MOSFET管IRFP450构成全桥电路实现信号的功率放大。试验结果表明：该系统的稳定性好,可调节磁场强度,能有效地提高电磁超声能量转化效率。     

变参量超声电机驱动电路的设计与分析

超声电机驱动电源一般是通过调占空比实现超声电机的控制.文中介绍一种由单片机控制可以同时实现调频、调占空比和调相位差的驱动与控制线路.实验结果表明该驱动源频率变化范围达20kHz～100kHz;相位差0°～90°可调;占空比0.1～0.5可调.     

三角波激励ECT测量电路

电容层析成像系统测量电路须有极高灵敏度及动态测量范围。提出一种采用三角波代替传统正弦波作为激励信号的方法,利用C/V转换电路的微分特性,使其输出为方波信号且幅值与被测电容值呈线性关系。瞬态仿真表明,电路的稳定时间缩短为0.65μs;此外,因其不需要相敏解调的环节,电容测量速率大幅提高,将其用于12电极ECT测量,可使测量速度提高到3124帧/s。实测结果表明,该电路的测量灵敏度峰峰值达0.8 V/pF,动态测量范围可达到69 dB。     

利用参量效应及反射差频波进行非线性参量B/A成像

引言 目前,超声成像仪器在医学诊断和治疗中的应用已经相当普遍,最常见的有B超、超声多普勒等,但是这些医疗仪器大都建立在线性假设的条件下,采用声阻抗、声速、声衰减等常见的线性参量进行成像.而实际上超声波在介质的传播过程中存在不容忽视的非线性效应,诸如波形畸变、声饱和、非线性附加衰减等这些非线性效应的存在将影响超声诊断的准确性和治疗的有效性[1].     

Parametrically driven nonlinear oscillator at a few-photon level

Abstract

We consider quantum dynamics of a parametrically driven anharmonic oscillator (PDAO) at a few-photon level. In this scheme the oscillatory mode is excited through the degenerate down-conversion process. This scheme could be experimentally realized in superconducting solid-state devices based on the nonlinearity of the Josephson junction or in cooled nano-mechanical oscillators. We investigate PDAO in the strong quantum regime that means strong Kerr-nonlinearity of the mode with respect to the mode’s dissipation for two cases of excitations: by a monochromatic driving field or by a train of Gaussian pulses. We demonstrate production of the nonclassical oscillatory states with two-fold symmetry in phase-space which are approximately close to the lower pure Fock states. Production of the superposition of the Fock states for time-intervals exceeding the characteristic time of decoherence and dissipation is also shown.     

On a driven nonlinear circuit and chaotic behaviour

Abstract

The chaotic behaviour of the sinusoidally driven nonlinear circuit proposed by Hunt is investigated. The results are compared with those from other driven nonlinear circuits.     

Analysis of a filter circuit for nonlinear loads

A capacitor is connected in parallel with a saturated core coil assembly (a nonlinear load) to reduce the magnetizing current. A linear reactor is connected in series with supply to reduce the distortion in supply current. This typical reactor capacitor filter system has been analyzed by an iterative procedure based on harmonic equivalent circuits. The analysis presented here predicts the harmonic resonance points of the circuit with good accuracy. The technique is applicable, in general, to any nonlinear load.     

Frequency domain analysis of nonlinear systems driven by multiharmonic signals

This paper examines the output properties of static power-series nonlinearities driven by periodic multiharmonic signals with emphasis given to their effect on linear frequency response function (FRF) measurements. The analysis is based on the classification of nonlinear distortions into harmonic and interharmonic contributions. The properties of harmonic contributions are examined in detail and explicit formulae are derived, by which the number of harmonic contributions generated at the test frequencies can be calculated for odd-order nonlinearities up to, and including, the ninth order. Although an analytic solution for any odd-order nonlinearity is still under investigation, a heuristic methodology is developed that solves this problem. It is shown that the derived formulae provide a useful tool in the examination of the behavior of FRF measurements in the presence of nonlinear distortions. Based on these formulae, different approaches in classifying nonlinear distortions are then compared with respect to their suitability in assessing the influence of system nonlinearities on linear FRF measurements.     

由电磁力激发的电机参数振动的分岔研究

将机械振动，非线性动力学与电机瞬变理论，电磁场理论的交叉课题相结合，建立了电机转子横向振动的非线性微分方程，并将方程约化为在参数激励作用下单自由度非线性动力系统，从非线性分岔理论的观点，分析机电耦联动力系统的特性是电机领域研究的焦点，研究了由电磁力激发的参数振动非线性系统的分岔问题，给出系统的分岔转迁集和分岔响应曲线，揭示了各种电磁参数及机械参数对共振的影响，得到了有价值的结果，可对实际电机系统的参数设计，稳定运行和故障诊断提供一定的理论依据。     

An improved lumped element nonlinear circuit model for a circular CMUT cell

This paper describes a correction and an extension in the previously published large signal equivalent circuit model for a circular capacitive micromachined ultrasonic transducer (CMUT) cell. The force model is rederived so that the energy and power is preserved in the equivalent circuit model. The model is able to predict the entire behavior of CMUT until the membrane touches the substrate. Many intrinsic properties of the CMUT cell, such as the collapse condition, collapse voltage, the voltage-displacement interrelation and the force equilibrium before and after collapse voltage in the presence of external static force, are obtained as a direct consequence of the model. The small signal equivalent circuit for any bias condition is obtained from the large signal model. The model can be implemented in circuit simulation tools and model predictions are in excellent agreement with finite element method simulations.     

参量激励驻孤波:从时间分岔到时空分岔

1引言 在理论上,孤立波的分岔行为及混沌运动已经得到了大量的研究.但是,理论工作大多限于数值模拟和计算,很难全局把握孤波的非线性动力学规律.实验研究鲜见报道,仅有的工作也难成体系,尤其是,孤立波向混沌过渡的途径及其物理机制问题一直没有得到很好的解决.